Instruction to load data up to a specified memory boundary indicated by the instruction

ABSTRACT

A Load to Block Boundary instruction is provided that loads a variable number of bytes of data into a register while ensuring that a specified memory boundary is not crossed. The boundary may be specified a number of ways, including, but not limited to, a variable value in the instruction text, a fixed instruction text value encoded in the opcode, or a register based boundary.

BACKGROUND

An aspect of the invention relates, in general, to data processing, and in particular, to loading data into registers.

Data processing includes various types of processing, including the loading of data into registers. The loading of data into a register includes, but is not limited to, the loading of character data, such as character data strings; integer data; or any other types of data. The data that is loaded is then capable of being used and/or manipulated.

Current instructions to perform various types of processing, including the loading of the data into registers, tend to be inefficient.

BRIEF SUMMARY

Shortcomings of the prior art are overcome and advantages are provided through the provision of a computer program product for executing a machine instruction. The computer program product includes a computer readable storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for performing a method. The method includes, for instance, obtaining, by a processor, a machine instruction for execution, the machine instruction being defined for computer execution according to a computer architecture, the machine instruction including: at least one opcode field to provide an opcode, the opcode identifying a load to block boundary operation; a register field to be used to designate a register, the register comprising a first operand; at least one field for locating a second operand in main memory; and executing the machine instruction, the execution including: only loading bytes of the first operand with corresponding bytes of the second operand that are within an instruction specified block of main memory.

Methods and systems relating to one or more aspects of the present invention are also described and claimed herein. Further, services relating to one or more aspects of the present invention are also described and may be claimed herein.

Additional features and advantages are realized through the techniques of the present invention. Other embodiments and aspects of the invention are described in detail herein and are considered a part of the claimed invention.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

One or more aspects of the present invention are particularly pointed out and distinctly claimed as examples in the claims at the conclusion of the specification. The foregoing and other objects, features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:

FIG. 1 depicts one example of a computing environment to incorporate and use one or more aspects of the present invention;

FIG. 2A depicts another example of a computing environment to incorporate and use one or more aspects of the present invention;

FIG. 2B depicts further details of the memory of FIG. 2A, in accordance with an aspect of the present invention;

FIG. 3 depicts one embodiment of a format of a Vector Load To Block Boundary instruction, in accordance with an aspect of the present invention;

FIG. 4 depicts one embodiment of logic associated with the Vector Load to Block Boundary instruction, in accordance with an aspect of the present invention;

FIG. 5 depicts one example of data to be loaded into a vector register, in accordance with an aspect of the present invention;

FIG. 6 depicts one example of a register file, in accordance with an aspect of the present invention;

FIG. 7 depicts one embodiment of a computer program product incorporating one or more aspects of the present invention;

FIG. 8 depicts one embodiment of a host computer system to incorporate and use one or more aspects of the present invention;

FIG. 9 depicts a further example of a computer system to incorporate and use one or more aspects of the present invention;

FIG. 10 depicts another example of a computer system comprising a computer network to incorporate and use one or more aspects of the present invention;

FIG. 11 depicts one embodiment of various elements of a computer system to incorporate and use one or more aspects of the present invention;

FIG. 12A depicts one embodiment of the execution unit of the computer system of FIG. 11 to incorporate and use one or more aspects of the present invention;

FIG. 12B depicts one embodiment of the branch unit of the computer system of FIG. 11 to incorporate and use one or more aspects of the present invention;

FIG. 12C depicts one embodiment of the load/store unit of the computer system of FIG. 11 to incorporate and use one or more aspects of the present invention; and

FIG. 13 depicts one embodiment of an emulated host computer system to incorporate and use one or more aspects of the present invention.

DETAILED DESCRIPTION

In accordance with an aspect of the present invention, a capability is provided for facilitating the loading of data in a register. As examples, the data includes character data, integer data and/or other types of data. Further, the register is a vector register or another type of register.

Character data, includes, but is not limited to, alphabetic characters, in any language; numeric digits; punctuation; and/or other symbols. The character data may or may not be strings of data. Associated with character data are standards, examples of which include, but are not limited to, ASCII (American Standard Code for Information Interchange); Unicode, including, but not limited to, UTF (Unicode Transformation Format) 8; UTF16; etc.

A vector register (also referred to as a vector) includes one or more elements, and each element is one, two or four bytes in length, as examples. Further, a vector operand is, for instance, a SIMD (Single Instruction, Multiple Data) operand having a plurality of elements. In other embodiments, elements can be of other sizes; and a vector operand need not be SIMD, and/or may include one element.

In one example, a Vector Load to Block Boundary instruction is provided that loads a variable number of bytes of data from memory into a vector register while ensuring that a specified boundary of the memory from which the data is being loaded is not crossed. The boundary may be specified explicitly by the instruction (e.g., a variable value in the instruction text, a fixed instruction text value encoded in the opcode, a register based boundary specified in the instruction, etc.); or the boundary may be dynamically determined by the machine. For instance, the instruction specifies that data is to be loaded to a page or cache boundary, and the machine determines the cache line or page size (e.g., looks-up in, for instance, a translation look aside buffer to determine the page size), and loads to that point.

As a further example, this instruction is also used to align data accesses to a selected boundary.

In one embodiment, the instruction only loads bytes of the vector register (a first operand) with corresponding bytes of a second operand that are within a block of main memory specified by the instruction. As used herein, a block of main memory (a.k.a., main storage) is any block of memory of a specified size. The specified size is also referred to as the boundary of the block, the boundary being the end of the block.

In a further embodiment, other types of registers are loaded. That is, the register being loaded is not a vector register but another type of register. In this context, the instruction is referred to as a Load to Block Boundary instruction, which is used to load data into a register.

One embodiment of a computing environment to incorporate and use one or more aspects of the present invention is described with reference to FIG. 1. A computing environment 100 includes, for instance, a processor 102 (e.g., a central processing unit), a memory 104 (e.g., main memory), and one or more input/output (I/O) devices and/or interfaces 106 coupled to one another via, for example, one or more buses 108 and/or other connections.

In one example, processor 102 is based on the z/Architecture offered by International Business Machines Corporation, and is part of a server, such as the System z server, which is also offered by International Business Machines Corporation and implements the z/Architecture. One embodiment of the z/Architecture is described in an IBM® publication entitled, “z/Architecture Principles of Operation,” IBM® Publication No. SA22-7832-08, Ninth Edition, August, 2010, which is hereby incorporated herein by reference in its entirety. In one example, the processor executes an operating system, such as z/OS, also offered by International Business Machines Corporation. IBM®, Z/ARCHITECTURE® and Z/OS® are registered trademarks of International Business Machines Corporation, Armonk, N.Y., USA. Other names used herein may be registered trademarks, trademarks, or product names of International Business Machines Corporation or other companies.

In a further embodiment, processor 102 is based on the Power Architecture offered by International Business Machines Corporation. One embodiment of the Power Architecture is described in “Power ISA™ Version 2.06 Revision B,” International Business Machines Corporation, Jul. 23, 2010, which is hereby incorporated herein by reference in its entirety. POWER ARCHITECTURE® is a registered trademark of International Business Machines Corporation.

In yet a further embodiment, processor 102 is based on an Intel architecture offered by Intel Corporation. One embodiment of the Intel architecture is described in “Intel® 64 and IA-32 Architectures Developer's Manual: Vol. 2B, Instructions Set Reference, A-L,” Order Number 253666-041US, December 2011, and “Intel® 64 and IA-32 Architectures Developer's Manual: Vol. 2B, Instructions Set Reference, M-Z,” Order Number 253667-041US, December 2011, each of which is hereby incorporated herein by reference in its entirety. Intel® is a registered trademark of Intel Corporation, Santa Clara, Calif.

Another embodiment of a computing environment to incorporate and use one or more aspects of the present invention is described with reference to FIG. 2A. In this example, a computing environment 200 includes, for instance, a native central processing unit 202, a memory 204, and one or more input/output devices and/or interfaces 206 coupled to one another via, for example, one or more buses 208 and/or other connections. As examples, computing environment 200 may include a PowerPC processor, a pSeries server or an xSeries server offered by International Business Machines Corporation, Armonk, N.Y.; an HP Superdome with Intel Itanium II processors offered by Hewlett Packard Co., Palo Alto, Calif.; and/or other machines based on architectures offered by International Business Machines Corporation, Hewlett Packard, Intel, Oracle, or others.

Native central processing unit 202 includes one or more native registers 210, such as one or more general purpose registers and/or one or more special purpose registers used during processing within the environment. These registers include information that represent the state of the environment at any particular point in time.

Moreover, native central processing unit 202 executes instructions and code that are stored in memory 204. In one particular example, the central processing unit executes emulator code 212 stored in memory 204. This code enables the processing environment configured in one architecture to emulate another architecture. For instance, emulator code 212 allows machines based on architectures other than the z/Architecture, such as PowerPC processors, pSeries servers, xSeries servers, HP Superdome servers or others, to emulate the z/Architecture and to execute software and instructions developed based on the z/Architecture.

Further details relating to emulator code 212 are described with reference to FIG. 2B. Guest instructions 250 comprise software instructions (e.g., machine instructions) that were developed to be executed in an architecture other than that of native CPU 202. For example, guest instructions 250 may have been designed to execute on a z/Architecture processor 102, but instead, are being emulated on native CPU 202, which may be, for example, an Intel Itanium II processor. In one example, emulator code 212 includes an instruction fetching unit 252 to obtain one or more guest instructions 250 from memory 204, and to optionally provide local buffering for the instructions obtained. It also includes an instruction translation routine 254 to determine the type of guest instruction that has been obtained and to translate the guest instruction into one or more corresponding native instructions 256. This translation includes, for instance, identifying the function to be performed by the guest instruction and choosing the native instruction(s) to perform that function.

Further, emulator 212 includes an emulation control routine 260 to cause the native instructions to be executed. Emulation control routine 260 may cause native CPU 202 to execute a routine of native instructions that emulate one or more previously obtained guest instructions and, at the conclusion of such execution, return control to the instruction fetch routine to emulate the obtaining of the next guest instruction or a group of guest instructions. Execution of the native instructions 256 may include loading data into a register from memory 204; storing data back to memory from a register; or performing some type of arithmetic or logic operation, as determined by the translation routine.

Each routine is, for instance, implemented in software, which is stored in memory and executed by native central processing unit 202. In other examples, one or more of the routines or operations are implemented in firmware, hardware, software or some combination thereof. The registers of the emulated processor may be emulated using registers 210 of the native CPU or by using locations in memory 204. In embodiments, guest instructions 250, native instructions 256 and emulator code 212 may reside in the same memory or may be disbursed among different memory devices.

As used herein, firmware includes, e.g., the microcode, millicode and/or macrocode of the processor. It includes, for instance, the hardware-level instructions and/or data structures used in implementation of higher level machine code. In one embodiment, it includes, for instance, proprietary code that is typically delivered as microcode that includes trusted software or microcode specific to the underlying hardware and controls operating system access to the system hardware.

In one example, a guest instruction 250 that is obtained, translated and executed is the instruction described herein. The instruction, which is of one architecture (e.g., the z/Architecture) is fetched from memory, translated and represented as a sequence of native instructions 256 of another architecture (e.g., PowerPC, pSeries, xSeries, Intel, etc.). These native instructions are then executed.

In one embodiment, the instruction described herein is a vector instruction, which is part of a vector facility, provided in accordance with an aspect of the present invention. The vector facility provides, for instance, fixed sized vectors ranging from one to sixteen elements. Each vector includes data which is operated on by vector instructions defined in the facility. In one embodiment, if a vector is made up of multiple elements, then each element is processed in parallel with the other elements. Instruction completion does not occur until processing of all the elements is complete.

As described herein, the vector instructions can be implemented as part of various architectures, including, but not limited to, the z/Architecture, Power, Intel, etc. Although an embodiment described herein is for the z/Architecture, the vector instructions and one or more aspects of the present invention may be based on many other architectures. The z/Architecture is only one example.

In one embodiment in which the vector facility is implemented as part of the z/Architecture, to use the vector registers and instructions, a vector enablement control and a register control in a specified control register (e.g., control register 0) are set to, for instance, one. If the vector facility is installed and a vector instruction is executed without the enablement controls set, a data exception is recognized. If the vector facility is not installed and a vector instruction is executed, an operation exception is recognized.

Vector data appears in storage, for instance, in the same left-to-right sequence as other data formats. Bits of a data format that are numbered 0-7 constitute the byte in the leftmost (lowest-numbered) byte location in storage, bits 8-15 form the byte in the next sequential location, and so on. In a further example, the vector data may appear in storage in another sequence, such as right-to-left.

Many of the vector instructions provided with the vector facility have a field of specified bits. This field, referred to as the register extension bit or RXB, includes the most significant bit for each of the vector register designated operands. Bits for register designations not specified by the instruction are to be reserved and set to zero.

In one example, the RXB field includes four bits (e.g., bits 0-3), and the bits are defined, as follows:

-   -   0—Most significant bit for the first vector register designation         of the instruction.     -   1—Most significant bit for the second vector register         designation of the instruction, if any.     -   2—Most significant bit for the third vector register designation         of the instruction, if any.     -   3—Most significant bit for the fourth vector register         designation of the instruction, if any.

Each bit is set to zero or one by, for instance, the assembler depending on the register number. For instance, for registers 0-15, the bit is set to 0; for registers 16-31, the bit is set to 1, etc.

In one embodiment, each RXB bit is an extension bit for a particular location in an instruction that includes one or more vector registers. For instance, in one or more vector instructions, bit 0 of RXB is an extension bit for location 8-11, which is assigned to, e.g., V₁; bit 1 of RXB is an extension bit for location 12-15, which is assigned to, e.g., V₂; and so forth.

In a further embodiment, the RXB field includes additional bits, and more than one bit is used as an extension for each vector or location.

One instruction, provided in accordance with an aspect of the present invention that includes the RXB field, is a Vector Load To Block Boundary instruction, an example of which is depicted in FIG. 3. In one example, the Vector Load To Block Boundary instruction 300 includes opcode fields 302 a (e.g., bits 0-7), 302 b (e.g., bits 40-47) indicating a Vector Load To Block Boundary operation; a vector register field 304 (e.g., bits 8-11) used to designate a vector register (V₁); an index field (X₂) 306 (e.g., bits 12-15); a base field (B₂) 308 (e.g., bits 16-19); a displacement field (D₂) 310 (e.g., bits 20-31); a mask field (M₃) 312 (e.g., bits 32-35); and an RXB field 316 (e.g., bits 36-39). Each of the fields 304-314, in one example, is separate and independent from the opcode field(s). Further, in one embodiment, they are separate and independent from one another; however, in other embodiments, more than one field may be combined. Further information on the use of these fields is described below.

In one example, selected bits (e.g., the first two bits) of the opcode designated by opcode field 302 a specify the length and format of the instruction. In this particular example, the length is three halfwords, and the format is a vector register-and-index-storage operation with an extended opcode field. The vector (V) field, along with its corresponding extension bit specified by RXB, designates a vector register. In particular, for vector registers, the register containing the operand is specified using, for instance, a four-bit field of the register field with the addition of the register extension bit (RXB) as the most significant bit. For instance, if the four bit field is 0110 and the extension bit is 0, then the five bit field 00110 indicates register number 6.

The subscript number associated with a field of the instruction denotes the operand to which the field applies. For instance, the subscript number 1 associated with V₁ denotes the first operand, and so forth. The register operand is one register in length, which is, for instance, 128 bits.

In one example, in a vector register-and-index storage operation instruction, the contents of general registers designated by the X₂ and B₂ fields are added to the contents of the D₂ field to form the second operand address. The displacement, D₂, for the Vector Load To Block Boundary instruction is treated as a 12 bit unsigned integer, in one example.

The M₃ field, in one embodiment, specifies a code that is used to signal the CPU as to the block boundary to load to. If a reserved value is specified, a specification exception is recognized. Example codes and corresponding values are as follows:

Code Boundary 0  64-Byte 1 128-Byte 2 256-Byte 3 512-Byte 4  1K-Byte 5  2K-Byte 6  4K-Byte

In execution of one embodiment of the Vector Load To Block Boundary (VLBB) instruction, preceding in one embodiment from left to right, the first operand (specified in the register designated by the V₁ field plus the extension bit) is loaded starting at the zero indexed byte element with bytes from the second operand. The second operand is a memory location designated by the second operand address (also referred to as a starting address). The loading starts from that memory location and continues to an ending address computed by the instruction (or processor), as described below. If a boundary condition is encountered, it is model-dependent on how the rest of the first operand is treated. Access exceptions are not recognized on bytes not loaded. In one example, bytes that are not loaded are unpredictable.

In the example instruction above, the starting address is determined by the index register value (X₂)+a base register value (B₂)+a displacement (D₂); however, in other embodiments, it is provided by a register value; an instruction address+instruction text specified offset; a register value+displacement; or a register value+index register value; as just some examples. Further, in one embodiment, the instruction does not include the RXB field. Instead, no extension is used or the extension is provided in another manner, such as from a control outside of the instruction, or provided as part of another field of the instruction.

Further details of one embodiment of processing the Vector Load to Block Boundary instruction are described with reference to FIG. 4. In one example, a processor of the computing environment is performing this logic.

In one embodiment, initially a boundary mask (BdyMask) is created, which is used to determine closeness to the specified boundary, STEP 400. To create the mask, in one example, a 2's complement negation of a boundary size (BdySize) 402 is taken creating boundary mask 404 (e.g., BdyMask=0−BdySize). The boundary size is provided, in one example, by the instruction (e.g., the M₃ field); or in another example, it is determined by the machine, as described herein.

Thereafter, a start address is computed, which indicates a location in memory from which loading is to begin, STEP 410. As examples, the start address 412 can be provided by a register value; an instruction address plus instruction text specified offset; a register value plus displacement; a register value plus index register value; or a register value plus index register value plus displacement. In the instruction provided herein, the start address is provided by the X₂ field, B₂ field and D₂ field. That is, contents of the registers designated by X₂ and B₂ are added to the displacement indicated by D₂ to provide the starting address. The above-indicated ways to compute a starting address are just examples; other examples are also possible.

Next, an end address is computed indicating where to stop loading from, STEP 420. Input to this computation is, for instance, boundary size 402, start address 412, vector size 414 (e.g., in bytes; e.g., 16), and boundary mask 404. In one example, end address 422 is computed as follows: EndAddress=min(StartAddress+(BdySize−(StartAddress &

BdyMask)),StartAddress+vec_size).

Thereafter, the first operand (i.e., the designated vector register) is loaded, starting at indexed byte 0, from memory commencing at the starting address and terminating at the ending address, STEP 430. This enables a variable number of bytes to be loaded from memory into a vector without crossing a designated memory boundary. For instance, if the memory boundary is at 64 bytes, and the starting address is at 58 bytes, then bytes 58-64 are loaded in the vector register.

One example of data to be loaded into a vector register, in accordance with an aspect of the present invention, is depicted in FIG. 5. As indicated, no data is loaded past the boundary designated by the dashed vertical line. The locations past the boundary are not accessible and no exception is taken. In one particular embodiment, the vector is loaded from left-to-right. However, in another embodiment, it can be loaded from right-to-left. In one embodiment, the direction of the vectors, left-to-right or right-to-left, is provided at runtime. For instance, the instruction accesses a register, status control or other entity that indicates the direction of processing is either left-to-right or right-to-left, as examples. In one embodiment, this direction control is not encoded as part of the instruction, but provided to the instruction at runtime.

Described above is one example of a load instruction. When loading data, such as string data, it is often not known if the string will end before a page boundary. The ability to load up to that boundary without crossing typically requires first checking for the end of the string. Some implementations may also have a penalty for crossing boundaries and software might want to avoid these. So, the ability to load up to several boundaries, is useful. An instruction is provided that loads a variable number of bytes into a vector register while ensuring that data from across a specified boundary is not loaded.

In one embodiment, there are 32 vector registers and other types of registers can map to a quadrant of the vector registers. For instance, as shown in FIG. 6, if there is a register file 600 that includes 32 vector registers 602 and each register is 128 bits in length, then 16 floating point registers 604, which are 64 bits in length, can overlay the vector registers. Thus, as an example, when floating point register 2 is modified, then vector register 2 is also modified. Other mappings for other types of registers is also possible.

Herein, memory, main memory, storage and main storage are used interchangeably, unless otherwise noted explicitly or by context.

Additional details relating to the vector facility, including examples of other instructions, are provided as part of this Detailed Description further below.

As will be appreciated by one skilled in the art, one or more aspects of the present invention may be embodied as a system, method or computer program product. Accordingly, one or more aspects of the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a “circuit,” “module” or “system”. Furthermore, one or more aspects of the present invention may take the form of a computer program product embodied in one or more computer readable medium(s) having computer readable program code embodied thereon.

Any combination of one or more computer readable medium(s) may be utilized. The computer readable medium may be a computer readable storage medium. A computer readable storage medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of the computer readable storage medium include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer readable storage medium may be any tangible medium that can contain or store a program for use by or in connection with an instruction execution system, apparatus, or device.

Referring now to FIG. 7, in one example, a computer program product 700 includes, for instance, one or more non-transitory computer readable storage media 702 to store computer readable program code means or logic 704 thereon to provide and facilitate one or more aspects of the present invention.

Program code embodied on a computer readable medium may be transmitted using an appropriate medium, including but not limited to wireless, wireline, optical fiber cable, RF, etc., or any suitable combination of the foregoing.

Computer program code for carrying out operations for one or more aspects of the present invention may be written in any combination of one or more programming languages, including an object oriented programming language, such as Java, Smalltalk, C++ or the like, and conventional procedural programming languages, such as the “C” programming language, assembler or similar programming languages. The program code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider).

One or more aspects of the present invention are described herein with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.

These computer program instructions may also be stored in a computer readable medium that can direct a computer, other programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the computer readable medium produce an article of manufacture including instructions which implement the function/act specified in the flowchart and/or block diagram block or blocks.

The computer program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide processes for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.

The flowchart and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to various embodiments of one or more aspects of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.

In addition to the above, one or more aspects of the present invention may be provided, offered, deployed, managed, serviced, etc. by a service provider who offers management of customer environments. For instance, the service provider can create, maintain, support, etc. computer code and/or a computer infrastructure that performs one or more aspects of the present invention for one or more customers. In return, the service provider may receive payment from the customer under a subscription and/or fee agreement, as examples. Additionally or alternatively, the service provider may receive payment from the sale of advertising content to one or more third parties.

In one aspect of the present invention, an application may be deployed for performing one or more aspects of the present invention. As one example, the deploying of an application comprises providing computer infrastructure operable to perform one or more aspects of the present invention.

As a further aspect of the present invention, a computing infrastructure may be deployed comprising integrating computer readable code into a computing system, in which the code in combination with the computing system is capable of performing one or more aspects of the present invention.

As yet a further aspect of the present invention, a process for integrating computing infrastructure comprising integrating computer readable code into a computer system may be provided. The computer system comprises a computer readable medium, in which the computer medium comprises one or more aspects of the present invention. The code in combination with the computer system is capable of performing one or more aspects of the present invention.

Although various embodiments are described above, these are only examples. For example, computing environments of other architectures can incorporate and use one or more aspects of the present invention. Further, registers of other sizes may be used, and changes to the instructions may be made without departing from the spirit of the present invention.

Further, other types of computing environments can benefit from one or more aspects of the present invention. As an example, a data processing system suitable for storing and/or executing program code is usable that includes at least two processors coupled directly or indirectly to memory elements through a system bus. The memory elements include, for instance, local memory employed during actual execution of the program code, bulk storage, and cache memory which provide temporary storage of at least some program code in order to reduce the number of times code must be retrieved from bulk storage during execution.

Input/Output or I/O devices (including, but not limited to, keyboards, displays, pointing devices, DASD, tape, CDs, DVDs, thumb drives and other memory media, etc.) can be coupled to the system either directly or through intervening I/O controllers. Network adapters may also be coupled to the system to enable the data processing system to become coupled to other data processing systems or remote printers or storage devices through intervening private or public networks. Modems, cable modems, and Ethernet cards are just a few of the available types of network adapters.

Referring to FIG. 8, representative components of a Host Computer system 5000 to implement one or more aspects of the present invention are portrayed. The representative host computer 5000 comprises one or more CPUs 5001 in communication with computer memory (i.e., central storage) 5002, as well as I/O interfaces to storage media devices 5011 and networks 5010 for communicating with other computers or SANs and the like. The CPU 5001 is compliant with an architecture having an architected instruction set and architected functionality. The CPU 5001 may have dynamic address translation (DAT) 5003 for transforming program addresses (virtual addresses) into real addresses of memory. A DAT typically includes a translation lookaside buffer (TLB) 5007 for caching translations so that later accesses to the block of computer memory 5002 do not require the delay of address translation. Typically, a cache 5009 is employed between computer memory 5002 and the processor 5001. The cache 5009 may be hierarchical having a large cache available to more than one CPU and smaller, faster (lower level) caches between the large cache and each CPU. In some implementations, the lower level caches are split to provide separate low level caches for instruction fetching and data accesses. In one embodiment, an instruction is fetched from memory 5002 by an instruction fetch unit 5004 via a cache 5009. The instruction is decoded in an instruction decode unit 5006 and dispatched (with other instructions in some embodiments) to instruction execution unit or units 5008. Typically several execution units 5008 are employed, for example an arithmetic execution unit, a floating point execution unit and a branch instruction execution unit. The instruction is executed by the execution unit, accessing operands from instruction specified registers or memory as needed. If an operand is to be accessed (loaded or stored) from memory 5002, a load/store unit 5005 typically handles the access under control of the instruction being executed. Instructions may be executed in hardware circuits or in internal microcode (firmware) or by a combination of both.

As noted, a computer system includes information in local (or main) storage, as well as addressing, protection, and reference and change recording. Some aspects of addressing include the format of addresses, the concept of address spaces, the various types of addresses, and the manner in which one type of address is translated to another type of address. Some of main storage includes permanently assigned storage locations. Main storage provides the system with directly addressable fast-access storage of data. Both data and programs are to be loaded into main storage (from input devices) before they can be processed.

Main storage may include one or more smaller, faster-access buffer storages, sometimes called caches. A cache is typically physically associated with a CPU or an I/O processor. The effects, except on performance, of the physical construction and use of distinct storage media are generally not observable by the program.

Separate caches may be maintained for instructions and for data operands. Information within a cache is maintained in contiguous bytes on an integral boundary called a cache block or cache line (or line, for short). A model may provide an EXTRACT CACHE ATTRIBUTE instruction which returns the size of a cache line in bytes. A model may also provide PREFETCH DATA and PREFETCH DATA RELATIVE LONG instructions which effects the prefetching of storage into the data or instruction cache or the releasing of data from the cache.

Storage is viewed as a long horizontal string of bits. For most operations, accesses to storage proceed in a left-to-right sequence. The string of bits is subdivided into units of eight bits. An eight-bit unit is called a byte, which is the basic building block of all information formats. Each byte location in storage is identified by a unique nonnegative integer, which is the address of that byte location or, simply, the byte address. Adjacent byte locations have consecutive addresses, starting with 0 on the left and proceeding in a left-to-right sequence. Addresses are unsigned binary integers and are 24, 31, or 64 bits.

Information is transmitted between storage and a CPU or a channel subsystem one byte, or a group of bytes, at a time. Unless otherwise specified, in, for instance, the z/Architecture, a group of bytes in storage is addressed by the leftmost byte of the group. The number of bytes in the group is either implied or explicitly specified by the operation to be performed. When used in a CPU operation, a group of bytes is called a field. Within each group of bytes, in, for instance, the z/Architecture, bits are numbered in a left-to-right sequence. In the z/Architecture, the leftmost bits are sometimes referred to as the “high-order” bits and the rightmost bits as the “low-order” bits. Bit numbers are not storage addresses, however. Only bytes can be addressed. To operate on individual bits of a byte in storage, the entire byte is accessed. The bits in a byte are numbered 0 through 7, from left to right (in, e.g., the z/Architecture). The bits in an address may be numbered 8-31 or 40-63 for 24-bit addresses, or 1-31 or 33-63 for 31-bit addresses; they are numbered 0-63 for 64-bit addresses. Within any other fixed-length format of multiple bytes, the bits making up the format are consecutively numbered starting from 0. For purposes of error detection, and in preferably for correction, one or more check bits may be transmitted with each byte or with a group of bytes. Such check bits are generated automatically by the machine and cannot be directly controlled by the program. Storage capacities are expressed in number of bytes. When the length of a storage-operand field is implied by the operation code of an instruction, the field is said to have a fixed length, which can be one, two, four, eight, or sixteen bytes. Larger fields may be implied for some instructions. When the length of a storage-operand field is not implied but is stated explicitly, the field is said to have a variable length. Variable-length operands can vary in length by increments of one byte (or with some instructions, in multiples of two bytes or other multiples). When information is placed in storage, the contents of only those byte locations are replaced that are included in the designated field, even though the width of the physical path to storage may be greater than the length of the field being stored.

Certain units of information are to be on an integral boundary in storage. A boundary is called integral for a unit of information when its storage address is a multiple of the length of the unit in bytes. Special names are given to fields of 2, 4, 8, and 16 bytes on an integral boundary. A halfword is a group of two consecutive bytes on a two-byte boundary and is the basic building block of instructions. A word is a group of four consecutive bytes on a four-byte boundary. A doubleword is a group of eight consecutive bytes on an eight-byte boundary. A quadword is a group of 16 consecutive bytes on a 16-byte boundary. When storage addresses designate halfwords, words, doublewords, and quadwords, the binary representation of the address contains one, two, three, or four rightmost zero bits, respectively. Instructions are to be on two-byte integral boundaries. The storage operands of most instructions do not have boundary-alignment requirements.

On devices that implement separate caches for instructions and data operands, a significant delay may be experienced if the program stores into a cache line from which instructions are subsequently fetched, regardless of whether the store alters the instructions that are subsequently fetched.

In one embodiment, the invention may be practiced by software (sometimes referred to licensed internal code, firmware, micro-code, milli-code, pico-code and the like, any of which would be consistent with one or more aspects the present invention). Referring to FIG. 8, software program code which embodies one or more aspects of the present invention may be accessed by processor 5001 of the host system 5000 from long-term storage media devices 5011, such as a CD-ROM drive, tape drive or hard drive. The software program code may be embodied on any of a variety of known media for use with a data processing system, such as a diskette, hard drive, or CD-ROM. The code may be distributed on such media, or may be distributed to users from computer memory 5002 or storage of one computer system over a network 5010 to other computer systems for use by users of such other systems.

The software program code includes an operating system which controls the function and interaction of the various computer components and one or more application programs. Program code is normally paged from storage media device 5011 to the relatively higher-speed computer storage 5002 where it is available for processing by processor 5001. The techniques and methods for embodying software program code in memory, on physical media, and/or distributing software code via networks are well known and will not be further discussed herein. Program code, when created and stored on a tangible medium (including but not limited to electronic memory modules (RAM), flash memory, Compact Discs (CDs), DVDs, Magnetic Tape and the like is often referred to as a “computer program product”. The computer program product medium is typically readable by a processing circuit preferably in a computer system for execution by the processing circuit.

FIG. 9 illustrates a representative workstation or server hardware system in which one or more aspects of the present invention may be practiced. The system 5020 of FIG. 9 comprises a representative base computer system 5021, such as a personal computer, a workstation or a server, including optional peripheral devices. The base computer system 5021 includes one or more processors 5026 and a bus employed to connect and enable communication between the processor(s) 5026 and the other components of the system 5021 in accordance with known techniques. The bus connects the processor 5026 to memory 5025 and long-term storage 5027 which can include a hard drive (including any of magnetic media, CD, DVD and Flash Memory for example) or a tape drive for example. The system 5021 might also include a user interface adapter, which connects the microprocessor 5026 via the bus to one or more interface devices, such as a keyboard 5024, a mouse 5023, a printer/scanner 5030 and/or other interface devices, which can be any user interface device, such as a touch sensitive screen, digitized entry pad, etc. The bus also connects a display device 5022, such as an LCD screen or monitor, to the microprocessor 5026 via a display adapter.

The system 5021 may communicate with other computers or networks of computers by way of a network adapter capable of communicating 5028 with a network 5029. Example network adapters are communications channels, token ring, Ethernet or modems. Alternatively, the system 5021 may communicate using a wireless interface, such as a CDPD (cellular digital packet data) card. The system 5021 may be associated with such other computers in a Local Area Network (LAN) or a Wide Area Network (WAN), or the system 5021 can be a client in a client/server arrangement with another computer, etc. All of these configurations, as well as the appropriate communications hardware and software, are known in the art.

FIG. 10 illustrates a data processing network 5040 in which one or more aspects of the present invention may be practiced. The data processing network 5040 may include a plurality of individual networks, such as a wireless network and a wired network, each of which may include a plurality of individual workstations 5041, 5042, 5043, 5044. Additionally, as those skilled in the art will appreciate, one or more LANs may be included, where a LAN may comprise a plurality of intelligent workstations coupled to a host processor.

Still referring to FIG. 10, the networks may also include mainframe computers or servers, such as a gateway computer (client server 5046) or application server (remote server 5048 which may access a data repository and may also be accessed directly from a workstation 5045). A gateway computer 5046 serves as a point of entry into each individual network. A gateway is needed when connecting one networking protocol to another. The gateway 5046 may be preferably coupled to another network (the Internet 5047 for example) by means of a communications link. The gateway 5046 may also be directly coupled to one or more workstations 5041, 5042, 5043, 5044 using a communications link. The gateway computer may be implemented utilizing an IBM eServer™ System z server available from International Business Machines Corporation.

Referring concurrently to FIG. 9 and FIG. 10, software programming code which may embody one or more aspects of the present invention may be accessed by the processor 5026 of the system 5020 from long-term storage media 5027, such as a CD-ROM drive or hard drive. The software programming code may be embodied on any of a variety of known media for use with a data processing system, such as a diskette, hard drive, or CD-ROM. The code may be distributed on such media, or may be distributed to users 5050, 5051 from the memory or storage of one computer system over a network to other computer systems for use by users of such other systems.

Alternatively, the programming code may be embodied in the memory 5025, and accessed by the processor 5026 using the processor bus. Such programming code includes an operating system which controls the function and interaction of the various computer components and one or more application programs 5032. Program code is normally paged from storage media 5027 to high-speed memory 5025 where it is available for processing by the processor 5026. The techniques and methods for embodying software programming code in memory, on physical media, and/or distributing software code via networks are well known and will not be further discussed herein. Program code, when created and stored on a tangible medium (including but not limited to electronic memory modules (RAM), flash memory, Compact Discs (CDs), DVDs, Magnetic Tape and the like is often referred to as a “computer program product”. The computer program product medium is typically readable by a processing circuit preferably in a computer system for execution by the processing circuit.

The cache that is most readily available to the processor (normally faster and smaller than other caches of the processor) is the lowest (L1 or level one) cache and main store (main memory) is the highest level cache (L3 if there are 3 levels). The lowest level cache is often divided into an instruction cache (I-Cache) holding machine instructions to be executed and a data cache (D-Cache) holding data operands.

Referring to FIG. 11, an exemplary processor embodiment is depicted for processor 5026. Typically one or more levels of cache 5053 are employed to buffer memory blocks in order to improve processor performance. The cache 5053 is a high speed buffer holding cache lines of memory data that are likely to be used. Typical cache lines are 64, 128 or 256 bytes of memory data. Separate caches are often employed for caching instructions than for caching data. Cache coherence (synchronization of copies of lines in memory and the caches) is often provided by various “snoop” algorithms well known in the art. Main memory storage 5025 of a processor system is often referred to as a cache. In a processor system having 4 levels of cache 5053, main storage 5025 is sometimes referred to as the level 5 (L5) cache since it is typically faster and only holds a portion of the non-volatile storage (DASD, tape etc) that is available to a computer system. Main storage 5025 “caches” pages of data paged in and out of the main storage 5025 by the operating system.

A program counter (instruction counter) 5061 keeps track of the address of the current instruction to be executed. A program counter in a z/Architecture processor is 64 bits and can be truncated to 31 or 24 bits to support prior addressing limits. A program counter is typically embodied in a PSW (program status word) of a computer such that it persists during context switching. Thus, a program in progress, having a program counter value, may be interrupted by, for example, the operating system (context switch from the program environment to the operating system environment). The PSW of the program maintains the program counter value while the program is not active, and the program counter (in the PSW) of the operating system is used while the operating system is executing. Typically, the program counter is incremented by an amount equal to the number of bytes of the current instruction. RISC (Reduced Instruction Set Computing) instructions are typically fixed length while CISC (Complex Instruction Set Computing) instructions are typically variable length. Instructions of the IBM z/Architecture are CISC instructions having a length of 2, 4 or 6 bytes. The Program counter 5061 is modified by either a context switch operation or a branch taken operation of a branch instruction for example. In a context switch operation, the current program counter value is saved in the program status word along with other state information about the program being executed (such as condition codes), and a new program counter value is loaded pointing to an instruction of a new program module to be executed. A branch taken operation is performed in order to permit the program to make decisions or loop within the program by loading the result of the branch instruction into the program counter 5061.

Typically an instruction fetch unit 5055 is employed to fetch instructions on behalf of the processor 5026. The fetch unit either fetches “next sequential instructions”, target instructions of branch taken instructions, or first instructions of a program following a context switch. Modern Instruction fetch units often employ prefetch techniques to speculatively prefetch instructions based on the likelihood that the prefetched instructions might be used. For example, a fetch unit may fetch 16 bytes of instruction that includes the next sequential instruction and additional bytes of further sequential instructions.

The fetched instructions are then executed by the processor 5026. In an embodiment, the fetched instruction(s) are passed to a dispatch unit 5056 of the fetch unit. The dispatch unit decodes the instruction(s) and forwards information about the decoded instruction(s) to appropriate units 5057, 5058, 5060. An execution unit 5057 will typically receive information about decoded arithmetic instructions from the instruction fetch unit 5055 and will perform arithmetic operations on operands according to the opcode of the instruction. Operands are provided to the execution unit 5057 preferably either from memory 5025, architected registers 5059 or from an immediate field of the instruction being executed. Results of the execution, when stored, are stored either in memory 5025, registers 5059 or in other machine hardware (such as control registers, PSW registers and the like).

A processor 5026 typically has one or more units 5057, 5058, 5060 for executing the function of the instruction. Referring to FIG. 12A, an execution unit 5057 may communicate with architected general registers 5059, a decode/dispatch unit 5056, a load store unit 5060, and other 5065 processor units by way of interfacing logic 5071. An execution unit 5057 may employ several register circuits 5067, 5068, 5069 to hold information that the arithmetic logic unit (ALU) 5066 will operate on. The ALU performs arithmetic operations such as add, subtract, multiply and divide as well as logical function such as and, or and exclusive- or (XOR), rotate and shift. Preferably the ALU supports specialized operations that are design dependent. Other circuits may provide other architected facilities 5072 including condition codes and recovery support logic for example. Typically the result of an ALU operation is held in an output register circuit 5070 which can forward the result to a variety of other processing functions. There are many arrangements of processor units, the present description is only intended to provide a representative understanding of one embodiment.

An ADD instruction for example would be executed in an execution unit 5057 having arithmetic and logical functionality while a floating point instruction for example would be executed in a floating point execution having specialized floating point capability. Preferably, an execution unit operates on operands identified by an instruction by performing an opcode defined function on the operands. For example, an ADD instruction may be executed by an execution unit 5057 on operands found in two registers 5059 identified by register fields of the instruction.

The execution unit 5057 performs the arithmetic addition on two operands and stores the result in a third operand where the third operand may be a third register or one of the two source registers. The execution unit preferably utilizes an Arithmetic Logic Unit (ALU) 5066 that is capable of performing a variety of logical functions such as Shift, Rotate, And, Or and XOR as well as a variety of algebraic functions including any of add, subtract, multiply, divide. Some ALUs 5066 are designed for scalar operations and some for floating point. Data may be Big Endian (where the least significant byte is at the highest byte address) or Little Endian (where the least significant byte is at the lowest byte address) depending on architecture. The IBM z/Architecture is Big Endian. Signed fields may be sign and magnitude, 1's complement or 2's complement depending on architecture. A 2's complement number is advantageous in that the ALU does not need to design a subtract capability since either a negative value or a positive value in 2's complement requires only an addition within the ALU. Numbers are commonly described in shorthand, where a 12 bit field defines an address of a 4,096 byte block and is commonly described as a 4 Kbyte (Kilo-byte) block, for example.

Referring to FIG. 12B, branch instruction information for executing a branch instruction is typically sent to a branch unit 5058 which often employs a branch prediction algorithm such as a branch history table 5082 to predict the outcome of the branch before other conditional operations are complete. The target of the current branch instruction will be fetched and speculatively executed before the conditional operations are complete. When the conditional operations are completed the speculatively executed branch instructions are either completed or discarded based on the conditions of the conditional operation and the speculated outcome. A typical branch instruction may test condition codes and branch to a target address if the condition codes meet the branch requirement of the branch instruction, a target address may be calculated based on several numbers including ones found in register fields or an immediate field of the instruction for example. The branch unit 5058 may employ an ALU 5074 having a plurality of input register circuits 5075, 5076, 5077 and an output register circuit 5080. The branch unit 5058 may communicate with general registers 5059, decode dispatch unit 5056 or other circuits 5073, for example.

The execution of a group of instructions can be interrupted for a variety of reasons including a context switch initiated by an operating system, a program exception or error causing a context switch, an I/O interruption signal causing a context switch or multi-threading activity of a plurality of programs (in a multi-threaded environment), for example. Preferably a context switch action saves state information about a currently executing program and then loads state information about another program being invoked. State information may be saved in hardware registers or in memory for example. State information preferably comprises a program counter value pointing to a next instruction to be executed, condition codes, memory translation information and architected register content. A context switch activity can be exercised by hardware circuits, application programs, operating system programs or firmware code (microcode, pico-code or licensed internal code (LIC)) alone or in combination.

A processor accesses operands according to instruction defined methods. The instruction may provide an immediate operand using the value of a portion of the instruction, may provide one or more register fields explicitly pointing to either general purpose registers or special purpose registers (floating point registers for example). The instruction may utilize implied registers identified by an opcode field as operands. The instruction may utilize memory locations for operands. A memory location of an operand may be provided by a register, an immediate field, or a combination of registers and immediate field as exemplified by the z/Architecture long displacement facility wherein the instruction defines a base register, an index register and an immediate field (displacement field) that are added together to provide the address of the operand in memory for example. Location herein typically implies a location in main memory (main storage) unless otherwise indicated.

Referring to FIG. 12C, a processor accesses storage using a load/store unit 5060. The load/store unit 5060 may perform a load operation by obtaining the address of the target operand in memory 5053 and loading the operand in a register 5059 or another memory 5053 location, or may perform a store operation by obtaining the address of the target operand in memory 5053 and storing data obtained from a register 5059 or another memory 5053 location in the target operand location in memory 5053. The load/store unit 5060 may be speculative and may access memory in a sequence that is out-of-order relative to instruction sequence, however the load/store unit 5060 is to maintain the appearance to programs that instructions were executed in order. A load/store unit 5060 may communicate with general registers 5059, decode/dispatch unit 5056, cache/memory interface 5053 or other elements 5083 and comprises various register circuits, ALUs 5085 and control logic 5090 to calculate storage addresses and to provide pipeline sequencing to keep operations in-order. Some operations may be out of order but the load/store unit provides functionality to make the out of order operations to appear to the program as having been performed in order, as is well known in the art.

Preferably addresses that an application program “sees” are often referred to as virtual addresses. Virtual addresses are sometimes referred to as “logical addresses” and “effective addresses”. These virtual addresses are virtual in that they are redirected to physical memory location by one of a variety of dynamic address translation (DAT) technologies including, but not limited to, simply prefixing a virtual address with an offset value, translating the virtual address via one or more translation tables, the translation tables preferably comprising at least a segment table and a page table alone or in combination, preferably, the segment table having an entry pointing to the page table. In the z/Architecture, a hierarchy of translation is provided including a region first table, a region second table, a region third table, a segment table and an optional page table. The performance of the address translation is often improved by utilizing a translation lookaside buffer (TLB) which comprises entries mapping a virtual address to an associated physical memory location. The entries are created when the DAT translates a virtual address using the translation tables. Subsequent use of the virtual address can then utilize the entry of the fast TLB rather than the slow sequential translation table accesses. TLB content may be managed by a variety of replacement algorithms including LRU (Least Recently used).

In the case where the processor is a processor of a multi-processor system, each processor has responsibility to keep shared resources, such as I/O, caches, TLBs and memory, interlocked for coherency. Typically, “snoop” technologies will be utilized in maintaining cache coherency. In a snoop environment, each cache line may be marked as being in any one of a shared state, an exclusive state, a changed state, an invalid state and the like in order to facilitate sharing.

I/O units 5054 (FIG. 11) provide the processor with means for attaching to peripheral devices including tape, disc, printers, displays, and networks for example. I/O units are often presented to the computer program by software drivers. In mainframes, such as the System z® from IBM®, channel adapters and open system adapters are I/O units of the mainframe that provide the communications between the operating system and peripheral devices.

Further, other types of computing environments can benefit from one or more aspects of the present invention. As an example, an environment may include an emulator (e.g., software or other emulation mechanisms), in which a particular architecture (including, for instance, instruction execution, architected functions, such as address translation, and architected registers) or a subset thereof is emulated (e.g., on a native computer system having a processor and memory). In such an environment, one or more emulation functions of the emulator can implement one or more aspects of the present invention, even though a computer executing the emulator may have a different architecture than the capabilities being emulated. As one example, in emulation mode, the specific instruction or operation being emulated is decoded, and an appropriate emulation function is built to implement the individual instruction or operation.

In an emulation environment, a host computer includes, for instance, a memory to store instructions and data; an instruction fetch unit to fetch instructions from memory and to optionally, provide local buffering for the fetched instruction; an instruction decode unit to receive the fetched instructions and to determine the type of instructions that have been fetched; and an instruction execution unit to execute the instructions. Execution may include loading data into a register from memory; storing data back to memory from a register; or performing some type of arithmetic or logical operation, as determined by the decode unit. In one example, each unit is implemented in software. For instance, the operations being performed by the units are implemented as one or more subroutines within emulator software.

More particularly, in a mainframe, architected machine instructions are used by programmers, usually today “C” programmers, often by way of a compiler application. These instructions stored in the storage medium may be executed natively in a z/Architecture IBM® Server, or alternatively in machines executing other architectures. They can be emulated in the existing and in future IBM® mainframe servers and on other machines of IBM® (e.g., Power Systems servers and System x® Servers). They can be executed in machines running Linux on a wide variety of machines using hardware manufactured by IBM®, Intel®, AMD™, and others. Besides execution on that hardware under a z/Architecture, Linux can be used as well as machines which use emulation by Hercules, UMX, or FSI (Fundamental Software, Inc), where generally execution is in an emulation mode. In emulation mode, emulation software is executed by a native processor to emulate the architecture of an emulated processor.

The native processor typically executes emulation software comprising either firmware or a native operating system to perform emulation of the emulated processor. The emulation software is responsible for fetching and executing instructions of the emulated processor architecture. The emulation software maintains an emulated program counter to keep track of instruction boundaries. The emulation software may fetch one or more emulated machine instructions at a time and convert the one or more emulated machine instructions to a corresponding group of native machine instructions for execution by the native processor. These converted instructions may be cached such that a faster conversion can be accomplished. Notwithstanding, the emulation software is to maintain the architecture rules of the emulated processor architecture so as to assure operating systems and applications written for the emulated processor operate correctly. Furthermore, the emulation software is to provide resources identified by the emulated processor architecture including, but not limited to, control registers, general purpose registers, floating point registers, dynamic address translation function including segment tables and page tables for example, interrupt mechanisms, context switch mechanisms, Time of Day (TOD) clocks and architected interfaces to I/O subsystems such that an operating system or an application program designed to run on the emulated processor, can be run on the native processor having the emulation software.

A specific instruction being emulated is decoded, and a subroutine is called to perform the function of the individual instruction. An emulation software function emulating a function of an emulated processor is implemented, for example, in a “C” subroutine or driver, or some other method of providing a driver for the specific hardware as will be within the skill of those in the art after understanding the description of the preferred embodiment. Various software and hardware emulation patents including, but not limited to U.S. Pat. No. 5,551,013, entitled “Multiprocessor for Hardware Emulation”, by Beausoleil et al.; and U.S. Pat. No. 6,009,261, entitled “Preprocessing of Stored Target Routines for Emulating Incompatible Instructions on a Target Processor”, by Scalzi et al; and U.S. Pat. No. 5,574,873, entitled “Decoding Guest Instruction to Directly Access Emulation Routines that Emulate the Guest Instructions”, by Davidian et al; and U.S. Pat. No. 6,308,255, entitled “Symmetrical Multiprocessing Bus and Chipset Used for Coprocessor Support Allowing Non-Native Code to Run in a System”, by Gorishek et al; and U.S. Pat. No. 6,463,582, entitled “Dynamic Optimizing Object Code Translator for Architecture Emulation and Dynamic Optimizing Object Code Translation Method”, by Lethin et al; and U.S. Pat. No. 5,790,825, entitled “Method for Emulating Guest Instructions on a Host Computer Through Dynamic Recompilation of Host Instructions”, by Eric Traut, each of which is hereby incorporated herein by reference in its entirety; and many others, illustrate a variety of known ways to achieve emulation of an instruction format architected for a different machine for a target machine available to those skilled in the art.

In FIG. 13, an example of an emulated host computer system 5092 is provided that emulates a host computer system 5000′ of a host architecture. In the emulated host computer system 5092, the host processor (CPU) 5091 is an emulated host processor (or virtual host processor) and comprises an emulation processor 5093 having a different native instruction set architecture than that of the processor 5091 of the host computer 5000′. The emulated host computer system 5092 has memory 5094 accessible to the emulation processor 5093. In the example embodiment, the memory 5094 is partitioned into a host computer memory 5096 portion and an emulation routines 5097 portion. The host computer memory 5096 is available to programs of the emulated host computer 5092 according to host computer architecture. The emulation processor 5093 executes native instructions of an architected instruction set of an architecture other than that of the emulated processor 5091, the native instructions obtained from emulation routines memory 5097, and may access a host instruction for execution from a program in host computer memory 5096 by employing one or more instruction(s) obtained in a sequence & access/decode routine which may decode the host instruction(s) accessed to determine a native instruction execution routine for emulating the function of the host instruction accessed. Other facilities that are defined for the host computer system 5000′ architecture may be emulated by architected facilities routines, including such facilities as general purpose registers, control registers, dynamic address translation and I/O subsystem support and processor cache, for example. The emulation routines may also take advantage of functions available in the emulation processor 5093 (such as general registers and dynamic translation of virtual addresses) to improve performance of the emulation routines. Special hardware and off-load engines may also be provided to assist the processor 5093 in emulating the function of the host computer 5000′.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising”, when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and/or groups thereof.

The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below, if any, are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of one or more aspects of the present invention has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the invention. The embodiment was chosen and described in order to best explain the principles of the invention and the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated. 

What is claimed is:
 1. A computer program product for executing a machine instruction in a central processing unit, the computer program product comprising: a non-transitory computer readable storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for performing a method comprising: obtaining, by a processor, a machine instruction for execution, the machine instruction being defined for computer execution according to a computer architecture, the machine instruction comprising: at least one opcode field to provide an opcode, the opcode identifying a load to block boundary operation; a register field to be used to designate a register, the register comprising a first operand; at least one field for locating a second operand in main memory; and a block boundary size indicator for a memory block of the second operand, the memory block being a segment of memory having a fixed and predefined boundary size that is architecturally defined by a system architecture; and executing the machine instruction, the execution comprising: loading from the memory block of the second operand a variable amount of data into the first operand while ensuring only data within the memory block is being loaded into the first operand, wherein the loading from the memory block starts at a starting address in the memory block of the second operand, the starting address provided by the machine instruction, and ends at an ending address, the loading comprising: determining a boundary mask based on the boundary size, the boundary mask for determining closeness of the starting address to a boundary of the memory block; determining an ending address at which loading is to stop, the determining comprising selecting between a first memory position and a second memory position, the first memory position determined based on the boundary size and on masking the starting address using the boundary mask, and the second memory position determined as the starting address plus a length of the first operand; and loading the amount of data into the first operand, the loading terminating at the ending address.
 2. The computer program product of claim 1, wherein the at least one field comprises a displacement field, a base field and an index field, the base field and index field for locating general registers having contents to be added to contents of the displacement field to form an address of the second operand, and wherein the machine instruction further comprises a mask field, the mask field specifying the block boundary size indicator.
 3. The computer program product of claim 2, wherein the block boundary is one block boundary of a plurality of block boundaries specifiable by the mask field.
 4. The computer program product of claim 1, wherein an address of the second operand is the starting address in memory from which data is to be loaded in the first operand.
 5. The computer program product of claim 1, wherein the loading comprises one of: loading the first operand from left to right, or loading the first operand from right to left.
 6. The computer program product of claim 5, wherein a direction of the loading is provided at runtime.
 7. The computer program product of claim 1, wherein the machine instruction further comprises an extension field to be used in designating one or more registers, and wherein the register field is combined with at least a portion of the extension field to designate the register.
 8. The computer program product of claim 1, wherein the loading the first operand begins at an indexed byte 0 of the first operand, and continues up to a maximum byte index of the register.
 9. The computer program product of claim 1, wherein the variable amount of data is a minimum of a number of bytes in the first operand or a number of bytes loaded up to the determined boundary of the memory block.
 10. A computer system for executing a machine instruction in a central processing unit, the computer system comprising: a memory; and a processor in communication with the memory, wherein the computer system is configured to perform a method, said method comprising: obtaining, by a processor, a machine instruction for execution, the machine instruction being defined for computer execution according to a computer architecture, the machine instruction comprising: at least one opcode field to provide an opcode, the opcode identifying a load to block boundary operation; a register field to be used to designate a register, the register comprising a first operand; at least one field for locating a second operand in main memory; and a block boundary size indicator for a memory block of the second operand, the memory block being a segment of memory having a fixed and predefined boundary size that is architecturally defined by a system architecture; and executing the machine instruction, the execution comprising: loading from the memory block of the second operand a variable amount of data into the first operand while ensuring only data within the memory block is being loaded into the first operand, wherein the loading from the memory block starts at a starting address in the memory block of the second operand, the starting address provided by the machine instruction, and ends at an ending address, the loading comprising: determining a boundary mask based on the boundary size, the boundary mask for determining closeness of the starting address to a boundary of the memory block; determining an ending address at which loading is to stop, the determining comprising selecting between a first memory position and a second memory position, the first memory position determined based on the boundary size and on masking the starting address using the boundary mask, and the second memory position determined as the starting address plus a length of the first operand; and loading the amount of data into the first operand, the loading terminating at the ending address.
 11. The computer system of claim 10, wherein the at least one field comprises a displacement field, a base field and an index field, the base field and index field for locating general registers having contents to be added to contents of the displacement field to form an address of the second operand, and wherein the machine instruction further comprises a mask field, the mask field specifying the block boundary size indicator.
 12. The computer system of claim 10, wherein an address of the second operand is the starting address in memory from which data is to be loaded in the first operand.
 13. The computer system of claim 10, wherein the loading comprises one of: loading the first operand from left to right, or loading the first operand from right to left.
 14. The computer system of claim 13, wherein a direction of the loading is provided at runtime.
 15. The computer system of claim 10, wherein the loading the first operand begins at an indexed byte 0 of the first operand, and continues up to a maximum byte index of the register.
 16. The computer system of claim 10, wherein the variable amount of data is a minimum of a number of bytes in the first operand or a number of bytes loaded up to the determined boundary of the memory block.
 17. The computer program product of claim 1, wherein the loading ends before the determined boundary of the memory block of the second operand. 